Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G77/00—Macromolecular compounds obtained by reactions forming a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon in the main chain of the macromolecule
  • C08G77/04—Polysiloxanes
  • C08G77/20—Polysiloxanes containing silicon bound to unsaturated aliphatic groups
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K5/00—Use of organic ingredients
  • C08K5/04—Oxygen-containing compounds
  • C08K5/14—Peroxides

Definitions

• This invention relates to a silicone elastomer composition possessing novel crosslinking points, and more particularly, to a silicone elastomer composition possessing two or more organo groups including at least five carbon atoms and a carbon-carbon double bond bonding to a silicon atom via at least one carbon atom as the crosslinking points thereof.
• a shaped article of silicone elastomer therefore, can be obtained by blending a vinyl group-containing polyorganosiloxane as a base polymer with an organic peroxide as a vulcanizer and molding the obtained blend, or blending with a polyorganohydrogensiloxane and a platinum compound and molding the obtained blend.
• the organic peroxides available as the aforementioned vulcanizer are divided into two types, acyl type which evolves carboxylic acids and non-acyl type which evolves alcohols.
• HAV oxygen-containing atmosphere
• the vulcanizer is one of only a small number of members selected from the acyl type organic peroxides, such as, for example, 2,4-dichlorobenzoyl peroxide or o-chlorobenzoyl peroxide.
• the 2,4-dichlorobenzoyl peroxide which is usable in HAV has the disadvantage that 2,4-dichlorobenzoic acid, the product of decomposition thereof, induces the phenomenon of blooming on the surface of the molded elastomer product and seriously impairs its outward appearance.
• the acyl type peroxides have the disadvantage that since these peroxides are transformed by decomposition into carboxylic acids, they have an adverse effect on the heat resistance of silicone elastomer.
• the non-acyl type peroxides which are transformed by decomposition into alcohols fail to give desired vulcanization by HAV, although they do refrain from producing any adverse effect on the silicone elastomer.
• a conventional silicone elastomer composition incorporates therein carbon black for the purpose of permitting production of an electroconductive silicone elastomer
• the vulcanization of the silicone elastomer composition by HAV cannot be accomplished by either a non-acyl type peroxide or an acyl type peroxide.
• the method which effects the desired molding by mixing a vinyl group-containing polyorganosiloxane with a polyorganohydrogensiloxane and subjecting the resultant mixture to addition reaction using a platinum compound as a catalyst.
• this method permits vulcanization to be performed by HAV, it has the disadvantage that the elastomer composition incorporating this catalyst is deficient in stability to withstand aging at room temperature and is solidified into elastomer before it is molded into a given shape.
• the platinum compound used as the catalyst is liable to be poisoned by sulfur or antioxidants which are generally used in most organic rubber composition.
• the sulfur and antioxidants which remain on the molding device may possibly inactivate the catalyst.
• the present inventors conducted a diligent study in search of a silicone elastomer capable of being vulcanized by HAV using a non-acyl type peroxide. They have consequently found a silicone elastomer composition possessing novel crosslinking points and accomplished this invention as a result.
• this invention relates to a silicone elastomer composition, comprising:
• the polyorganosiloxane (A) to be used in the present invention is represented by the general formula: ##STR1## It may contain some R SiO 3/2 units or SiO 2 units in the structure thereof.
• R 2 and R 3 stand for the same or different monovalent organic groups to be selected from substituted and unsubstituted monovalent hydrocarbon groups.
• R 1 stands for an organic group selected from the same class of monovalent hydrocarbon groups as R 2 and R 3 , and the R 1 s may also be partly or wholly hydroxyl groups or alkoxy groups.
• the monovalent hydrocarbon groups include alkyl groups such as methyl, ethyl, propyl, hexyl, and decyl groups; alkenyl groups such as vinyl and allyl groups; aryl groups such as phenyl and tolyl groups; aralkyl groups such as ⁇ -phenylethyl and ⁇ -phenylpropyl groups; and substituted hydrocarbon groups such as chloromethyl, cyanoethyl, trifluoropropyl, and chlorophenyl groups.
• alkyl groups such as methyl, ethyl, propyl, hexyl, and decyl groups
• alkenyl groups such as vinyl and allyl groups
• aryl groups such as phenyl and tolyl groups
• aralkyl groups such as ⁇ -phenylethyl and ⁇ -phenylpropyl groups
• substituted hydrocarbon groups such as chloromethyl, cyanoethyl, trifluoro
• the polyorganosiloxane (A) in the silicone elastomer composition is required to contain in the structure thereof at least two hydrocarbon groups possessing at least five carbon atoms and possessing a carbon-carbon double bond bonding to a silicon atom via at least one carbon atom.
• hydrocarbon groups include ethylidene norbornyl, methylene norbornyl, dicyclopentenyl, 4-pentenyl, 4-hexenyl, and cyclooctenyl groups.
• Such hydrocarbon groups can be of just one species or two or more species. From the standpoint of availability of raw material and reactivity of double bond, alkylidene norbornyl groups prove to be particularly desirable.
• the silicone elastomer composition of this invention cannot be vulcanized by HAV using an alkyl type peroxide when the polyorganosiloxane contains zero or just one hydrocarbon group possessing at least five carbon atoms and a carbon-carbon double bond bonding to a silicon atom via at least one carbon atom within the molecular unit.
• the polyorganoxiloxane is required to contain at least two such hydrocarbon groups per molecule.
• the number of the hydrocarbon groups in the molecular unit had no upper limit in particular.
• these hydrocarbon groups should be present in a concentration of 0.05 to 5 mol % based on all the organic groups bonded to silicon atoms in the molecule.
• the positions at which these groups are attached are not specifically limited.
• the groups may be bonded to silicon atoms either in the internal part or at the terminal units of the molecular chain.
• the number of organic groups bonded to silicon atoms of polyorganosiloxane (A) is in the range of 1.98 to 2.02 per silicon atom, on average. If the number of organic groups is less than 1.98, the resultant silicone elastomer composition fails to constitute a satisfactory elastomer. If the number exceeds 2.02, the polyorganosiloxane cannot be obtained with a polymerization degree exceeding 100.
• the polymerization degree (n+1) of polyorganosiloxane (A) is required to exceed 100, preferably 1,000.
• the polymerization degree is preferably in the range of 2,000 to 20,000.
• the inorganic filler (B) used in this invention is intended as a component for imparting various properties, particularly mechanical strength, to shaped articles of silicone elastomer obtained from the composition of the present invention.
• the specific surface area of the inorganic filler is required to exceed 50 m 2 /g and desirably falls in the range of 100 to 300 m 2 /g.
• inorganic fillers answering the foregoing description are reinforcing silica such as fumed silica and precipitated silica, and various types of carbon black such as furnace black, channel black, thermal black, and acetylene black which are usable for particular purposes.
• the inorganic filler can be used in its unmodified form or it may be given a surface treatment as with an organosilicon compound, an organic resin acid, or an organic resin acid salt before it is put to use.
• the amount of the inorganic filler (B) used in the composition is in the range of 5 to 200 parts by weight per 100 parts by weight of polyorganosiloxane (A). If the amount of (B) is less than 5 parts by weight, the reinforcement produced is not sufficient. If it exceeds 200 parts by weight, the workability of the composition is impaired.
• the organic peroxide (C) used in this invention is a vulcanizer intended to cure the composition containing polyorganosiloxane (A) and inorganic filler (B).
• organic peroxide include acyl type peroxides such as benzoyl peroxide, p-chlorobenzoyl peroxide, o-chlorobenzoyl peroxide, and 2,4-dichlorobenzoyl peroxide, and non-acyl type peroxides such as di-t-butyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy) hexane, 2,5-dimethyl-2,5-di(t-butylperoxy)-3-hexine, 1,3-bis(t-butylperoxypropyl)-benzene, 1,1-di(t-butylperoxy)-3,5,5-trimethyl cyclohexane, t-butyl- peroxybenzoate, t-butyl peroxybenzoate, t-butyl peroxybenzoate, t-butyl peroxybenzoate, t-butyl peroxybenzoate
• the amount of organic peroxide (C) to be incorporated is in the range of 0.05 to 15 parts by weight per 100 parts by weight of polyorganosiloxane (A). If the amount of organic peroxide (C) incorporated is less than 0.05 part by weight, the vulcanization is not sufficiently effected. If this amount exceeds 15 parts by weight, the excess of the organic peroxide brings about no special effect and does harm to the physical properties of the molded silicone elastomer product.
• the silicone elastomer composition of the present invention permits a vinyl group-containing polysiloxane such as polymethylvinylsiloxane or polymethylphenylvinylsiloxane to be used therein as a base polymer in combination with component (A).
• the silicone elastomer composition may also incorporate ground quarts, diatomaceous earth, titanium dioxide, aluminum oxide, zinc oxide, magnesium oxide, magnesium carbonate, calcium carbonate, magnesium silicate, aluminum sulfate, calcium sulfate, barium sulfate, mica, asbestos, and glass powder. It may further incorporate therein a heat-resistance improver, a flame retardant, a vulcanization accelerator, a processing acid, coloring matter, etc. known to the art.
• the silicone elastomer composition of this invention is obtained by putting together the aforementioned components (A) through (C) and optionally various additives and homogeneously kneading them. This silicone elastomer composition, on exposure to heat, is turned into an elastomer.
• a mixture consisting of 296 parts of octamethylcyclotetrasiloxane, 16.8 parts of heptamethyl ethylidene norbornyl cyclotetrasiloxane, and 0.16 part of decamethyltetrasiloxane was heated at 140° to 150° C. and, with the addition of 0.007 part of potassium hydroxide, caused to polymerize for 15 hours, and then neutralized by addition of 0.004 part of phosphoric acid.
• the product thus obtained was polyorganosioxane containing 1 mol % of methyl ethylidene norbornyl siloxy units and having a polymerization degree of 8,000.
• test specimen about 25 ⁇ 50 mm in area was immediately cut off the rolled sheet and suspended in a hot air drier at 250° C. for five minutes to undergo HAV.
• the elastomer piece so produced was visually inspected as to condition of surface finish. The results are shown in Table 1.
• Comparative samples No. 1-No. 4 (Comparative Experiments 1-4) were prepared, which consist of the same as silicone elastomer compositions Examples 1-4 except using a polyorganosiloxane containing 0.2 mol % or 1.0 mol % of methylvinyl siloxane units and having a polymerization degree of 8,000 prepared by heating a mixture consisting of 296 parts of octamethylcyclotetrasiloxane, 0.69 part or 3.5 parts of tetramethyltetravinylsiloxane and 0.16 part of decamethyltetrasiloxane at 140° to 150° C.
• Example 1-4 100 parts of the ethylidene norbornyl group-containing polyorganosiloxane obtained in Example 1-4 and 50 parts of acetylene black having a specific surface area of 70 m 2 /g (produced by Denki Kagaku Kogyo Co., Ltd. and sold under the trademark "Denka Black") were thoroughly kneaded.
• the resultant mixture was further mixed with varying amounts of organic peroxide as indicated in Table 2, to produce silicone elastomer composition samples, No. 5-6 (Examples 5-6).
• the samples were subjected to press vulcanization at a press temperature of 170° C.
• silicone elastomer composition samples No. 5-No. 7 (Comparative Experiments 5-7) were prepared by using the same composition as described above, except that the polyorganosiloxane having 0.2 mol % or 1.0 mol % of methylvinyl siloxy units and having a polymerization degree of 8,000 similar to the polyorganosiloxane used in Comparative Experiments 1-4. They were similarly tested. The results are shown in Table 2. Comparative sample No. 5 used polyorganosiloxane containing 0.2 mol % of methylvinyl siloxy units and Comparative samples No. 6 and No. 7 each contained 1.0 mol % of methylvinyl siloxy units.
• a mixture of 296 parts of octamethylcyclotetrasiloxane, 5.0 part of hexamethyl di(ethylidene norbornyl) cyclotetrasiloxane, 0.70 part of tetramethyltetravinylcyclotetrasiloxane, and 0.25 part of decamethyltetrasiloxane was heated to 140° to 150° C. and, with the addition of 0.007 part of potassium hydroxide, subjected to polymerization for 15 hours, and neutralized by addition of 0.004 part of posphoric acid.
• the product so obtained was a polyorganosiloxane containing 0.5 mol % of methylethylidene norbornyl siloxy units and 0.2 mol % of methylvinyl siloxy units and having a polymerization degree of 5,000.
• the product so obtained was a polyorganosiloxane containing 1.0 mol % of methyl ethylidene norbornyl siloxy units, 0.2 mol % of methylvinyl siloxy units, and 5.0 mol % diphenyl siloxy units, and having a polymerization degree of 6,000.
• This sample was press vulcanized under a pressure of 150 kgf/cm 2 for 10 minutes at a press temperature of 170° C., to produce a sheet of elastomer 2 mm in thickness.
• This sheet was subjected to post-vulcanization at 200 C. for four hours and then tested for hardness, tensile strength, and elongation by the procedure specified by JIS C 2123. The results are shown in Table 4.
• the silicone elastomer composition sample no. 11 was carefully roll-milled to remove entrapped bubbles to produce a sheet about 5 mm in thickness.
• a test piece about 25 ⁇ 50 mm in area was immediately cut out of the sheet and suspended in a hot air drier at 250° C. for five minutes to undergo HAV. The resultant elastomer piece was visually inspected for surface finish condition. The results are shown in Table 4.
• a mixture consisting of 296 parts of octamethylcyclotetrasiloxane, 13.7 parts of heptamethyl dicyclopentenyl cyclotetrasiloxane, and 0.13 part of decamethyltetrasiloxane was heated to 140° to 150° C. and, with the addition of 0.007 part of potassium hydroxide, subjected to polymerization for 15 hours, and then neutralized by addition of 0.004 part of phosphoric acid.
• the product so obtained was a polyorganosiloxane containing 0.8 mol % of methyldicyclopentenyl siloxy units and having a polymerization degree of 10,000.
• This sheet was subjected to post-vulcanization at 200 C for four hours and then tested for hardness, tensile strength, and elongation by the procedures specified by JIS C 2123. The results are shown in Table 4.
• the silicone elastomer composition sample, No. 12 was carefully roll-milled to remove entrapped bubbles to produce a sheet of elastomer about 5 mm in thickness.
• a test piece about 25 ⁇ 50 mm was immediately cut out of the sheet and suspended in a hot air drier at 250° C. for five minutes to undergo HAV. The elastomer piece thus obtained was visually inspected for surface finish condition. The results are shown in Table 4.
• a mixture consisting of 296 parts of octamethylcyclotetrasiloxane, 7.4 parts of heptamethyl-4(4-hexenyl)cyclotetrasiloxane, and 0.25 part of decamethyltetrasiloxane was heated to 140° to 150° C. and, with the addition of 0.007 part of potassium hydroxide, subjected to polymerization for 15 hours, and neutralized by addition of 0.004 part of phosphoric acid.
• the product so obtained was a polyorganosiloxane containing 0.5 mol % of methyl-(4-hexenyl)-siloxy units and having a polymerization degree of 5,000.
• This silicone elastomer composition sample No. 13 was carefully roll-milled to remove entrapped bubbles to produce a sheet about 5 mm in thickness. A test piece about 25 ⁇ 50 mm in area was immerdiately cut out of the sheet and suspended in a hot air drier at 250° C. for five minutes to undergo HAV. The elastomer piece so obtained was visually inspected for surface finish condition. The results are shown in Table 4.
• the polymethyl (ethylidene norbornyl)siloxane is superior to the conventional polymethylvinylsiloxane in co-vulcanizing property and, consequently, in mechanical strength. It is seen from example 16 that the polymethyl(ethylidene norbornyl)siloxane is more effective than polymethylvinyl siloxane alone is used.
• Sheets 2 mm in thickness were prepared, which consists of the same as compositions Examples 11, 13 except using a polymethyl(dicyclo pentenyl)siloxane or a polymetyl(4-hexenyl)siloxane, in the place of the aforementioned polymethyl(ethylidene norbornyl)siloxanes. These samples were similarly tested. The results are shown in Table 6.
• the silicone elastomer composition of this invention can be sufficiently vulcanized without reference to particular combination between the organic peroxide and the method of vulcanization. Even when the silicone elastomer composition of this invention incorporates carbon black for the purpose of producing an electroconductive silicon elastomer, it can be satisfactorily subjected to HAV using a non-acyl type peroxide.
• the silicone elastomer composition of this invention finds utility in application to tubes, molded articles of profile extrusion, packings, and gaskets as well as sheathes for electric cables.

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• 1984
  • 1984-10-22 JP JP59221540A patent/JPS6198763A/ja active Granted
• 1985
  • 1985-10-21 EP EP85113341A patent/EP0180843B1/en not_active Expired
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